JPH02225105A - Radial tire for high speed heavy load - Google Patents

Abstract

PURPOSE:To improve durability of a bead part and increase a critical speed for causing generation of standing wave by setting the equatorial height of a belt layer larger than an outer end height, while setting a belt camber amount which is a difference between those heights to have a specified rate in relation to a belt width. CONSTITUTION:An equatorial height H1 from a bead bottom surface in a radial direction in an equatorial point P1 where the radial direction inner surface E of a belt layer 10 crosses a tire equatorial surface CO, is set larger than the height of a point at the outer most end, in a tire axial direction, in an inner surface E, namely, an outer end height H2 which is a height in a radial direction in the outer end point P2 of the belt 10. Further, a belt camber amount H which is a difference between the equatorial height H1 and the outer end height H2, is set to more than 6% of a belt width W which is the length of a tire in its axial direction between the outer end points P2. In addition, a carcass is curved along the inner surface E, and a curvature radius R1 passing through the inner surface F of the central line is set smaller in comparison with conventional curvature radii R1a, R1b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radial tire for high-speed heavy loads that can increase the critical speed for generating standing waves and improve the durability of the bead portion.

[Conventional technology]

Radial tires for high speed heavy loads, especially aircraft tires,
In recent years, as aircraft have become larger and their flight speeds have increased, operating speeds and operating loads have increased, so for safe takeoff and landing,
Great durability is required.

In addition, aircraft tires: ■ In order to effectively reduce the impact when an aircraft takes off and lands on a runway, the amount of tire deflection under load is, for example, 28.
~38%, which is extremely large, and therefore able to withstand large repeated deformations.

■ As aircraft speed increases, the speeds associated with take-off and landing increase, and therefore, aircraft must withstand high-speed rotation under heavy loads and large deformations.

■ It must withstand the taxi conditions in which a heavy load is applied over a relatively long period of time, even though the vehicle is moving at low speeds between the runway and the gate.

■ To reduce the weight of airplanes, per unit weight of tires,
Approximately 130 to 360 times the load (approximately 50 times the load on normal tires, and due to this, the load is approximately 10 to 16k)
Extremely high internal pressure such as g/c- is applied.

Tires are required to have the durability of each part of the tire, such as wear resistance, anti-rolling properties, and low heat generation, while satisfying the following characteristics.

On the other hand, as such aircraft tires, those having a cross-ply structure in which carcass cords are arranged so as to cross each other between plies are often used.

However, the rigidity of the tread part is low and the weight is large, which makes it unfavorable in terms of wear resistance and heat generation (because of the remarkable performance improvement of large jet aircraft in recent years, cross-ply structures are not suitable). has limitations in its use.

Therefore, in recent years, radial tires have been developed that have a so-called radial or semi-radial structure in which carcass cords are arranged in the radial direction of the tire, and belt stones made of highly elastic belt cords that are inclined at a small angle with respect to the tire equator are placed on the radial outside of the carcass. is being used.

[Problem to be solved by the invention]

However, it has been found that in aircraft tires having such a radial structure, the durability of the bead portion is relatively low compared to the durability of the entire tire.

It has also become clear that standing waves occur relatively.

Regarding the durability of the bead part, since the amount of radial deflection of the tire under load is large, about 28 to 35%, as described above, the carcass cord of the carcass A of the bead part is as shown in Fig. 8. It is clear that compressive stress acts on the portion folded around the bead core B, and a tensile force that pulls the carcass cord is generated on the inside in the axial direction of the tire.

On the other hand, it has been found that damage to the bead portion occurs near the upper end of the rim flange C. This is because the bead part collapses onto the upper piece of the upper end of the rim flange C that extends outward from the tire axis, causing compression due to sudden bending at that part, causing compressive stress concentration to occur in that part, and Drum tests revealed that the carcass cord was broken due to repeated compressive strain due to the large compressive stress acting on the carcass cord due to fatigue, and the broken end caused local concentration of compressive stress, causing damage to the bead part. It was revealed from the results. Note that this bending increases the contact pressure of the bead portion on the upper piece, and as the contact pressure increases, the compressive stress and damage increase.

Furthermore, the standing wave is a waving phenomenon that occurs in the tread part when the tire is running, and such waving in the tread part impairs tire durability, and also excites the bead part by passing through the sidewall part. , reducing its durability.

In addition, heavy-load high-speed radial tires for aircraft etc., as mentioned above, suffer from large tire deformation and take-off and landing speeds of 300)
Such standing waves are more likely to occur due to the high speed exceeding s/hour. As is well known, the standing wave in a radial tire is determined by the following equation (1).

Vc-T/a +2 depth 71/m - (1) where, ■ CC standing wave generation critical speed m mass of unit length of Nidred part El in-plane bending rigidity of tire of Nidred part T: belt tension k; carcass is the spring constant of

Equation (1) was obtained assuming that the belt layer is an infinite beam supported elastically by the carcass, and in order to increase the critical velocity Vc for generating standing waves, the mass m must be decreased. It can be seen that, on the other hand, the rigidity E1, belt tension T, and carcass spring constant k may be increased.

Here, the natural frequency of the belt is increased without reducing ff1m, and the critical speed Vc for generating a standing wave is calculated.
In order to increase the tension, a large tension T is applied to the belt by internal pressure filling.
It has been proven that this increases the apparent tire in-plane bending stiffness El of the tread portion and increases the critical speed Vc.

Moreover, although the above formula (1) assumes that a uniform tension T acts on the belt layer, the bulge in the tire equator region, the so-called crown portion of the tread region, is particularly large.
It has also been found through experiments that relatively increasing the belt tension T in this portion is effective in increasing the critical speed of the standing wave.

To this end, it is best to make the inner radius of the tread part, especially the belt layer, smaller than that of conventional tires, and to increase the amount of belt camber. When it is made approximately equal to , it also helps to reduce the contact pressure with the flange of the end part,
It has also been found that it has the effect of increasing the durability of the bead portion.

Furthermore, it has also been found that such an increase in the bulge in the round portion has the effect of helping to equalize the ground pressure distribution on the tread surface.

An object of the present invention is to provide a high-speed heavy-load radial tire that can enhance the durability of the bead portion and increase the critical speed for generating standing waves.

[Means to solve the problem]

The present invention is characterized in that it extends from the tread part to the sidewall part, turns back at the bead core of the bead part, and is 70° with respect to the tire equator.
A carcass consisting of one or more carcass plies having a carcass cord inclined at an angle of 90 degrees to 90 degrees, and a belt layer using a plurality of belt plies disposed radially outside the carcass and inside the tread portion, When installed on a regular rim and filled with regular internal pressure, the radial height Hl, which is the radial height at the point where the radial inner surface of the belt layer intersects with the tire equatorial plane, is the axially outermost point of the inner surface of the tire. Outer end height H2 which is the radial height at the end
and the difference between the equator height Hl and the outer edge height H2 (Hl
-82), the belt camber amount H is the belt width W, which is the length in the tire axial direction between the outer ends of the inner surface of the belt layer.
This is a radial tire for high-speed, heavy-duty use with a fuel efficiency of 6% or more.

[Effect]

As shown in Figure 1 showing the right half of the tire cross section, and Figure 2 showing the belt layer and carcass center line in comparison with a conventional tire, the belt camber in the standard state with tire 1 mounted on a regular rim and filled with the regular internal pressure. - The amount H is 6% or more of the belt width W. As a result, on the inner surface E of the belt layer 10, the carcass 7 is curved along the inner surface, so that the radius of curvature R1 passing through the inner surface F of the center line of the carcass 7 along the inner surface is changed by the broken line in FIG. , the radius of curvature R1a of the curved surfaces Fa and Fb of the conventional tires IA and IB shown by the - point tW line
, R1b. As a result, in the tire 1 of the present invention, the crown portion 20 protrudes and swells relatively outward compared to the shoulder portion 21, and therefore, the belt tension due to the centrifugal force of the crown portion 20 that acts during high speed rotation. T is relatively larger than the belt tension T in the shoulder portion 21 due to the large radius.

As described above, this increase in belt tension at the crown portion 20 increases the critical speed of standing waves and suppresses their occurrence.

Further, reducing the radius of curvature R1 in this way means that the radius of curvature R1 along the inner surface E of the belt layer 10 is reduced as shown in the figure.
A curved surface G with a radius of curvature R2 that is smoothly continuous with the curved surface F and continues from the sidewall part 4 to the bead core 2 is located inward of the tire from the curved surfaces Ga and Gb of the conventional tire, and contacts the bead core 2 in the tire axial direction at the tangent 11At. The angle formed with the gland becomes larger than the tangents ta and tb of the conventional product. This is defined as a curve based on the natural equilibrium shape theory in which the curved surfaces G, Ga, and Gb are smoothly connected between the curved surfaces F, Fa, and Fb and the bead portion 3, and these curved surfaces F, Fa, and Fb are - radius of curvature R2, R2a, R2
This comes from the fact that b. Therefore, when the bead portion 3 collapses due to the deformation of the bead portion 3 due to the load on the tire, the curved surface F of the carcass 7 exists inside the tire, so compared to the carcass of a conventional tire, the curved surface F of the carcass 7 The upper end of the parallel rim flange C is prevented from collapsing into the upper piece, and the degree of bending is reduced. Note that this makes it possible to reduce the contact pressure with the upper piece. This reduction in the contact pressure between the throat part 3 and the rim flange reduces the bending stress acting on the bead, and the associated compressive stress acting on the folded part of the carcass, improving the durability of the bead. It becomes Shirokoto.

Furthermore, when an extensible elastic cord with a large elongation under load is used as the carcass cord, the carcass cord can be filled with internal pressure and given a high elongation in advance to impart tensile force. Such tensile force reduces the compressive stress acting on the carcass cord at the rim flange side portion of the bead portion.

Therefore, generation of local stress due to deformation due to compression, etc., and furthermore, breakage due to fatigue can be prevented, the occurrence of repeated stress concentration in the bead portion can be reduced, and the durability of the bead portion can be improved.

Furthermore, due to normal internal pressure filling, the amount of expansion of the tread portion, especially the crown portion 20, increases, increasing the tension T of the belt layer in this portion, and increasing the apparent rigidity E of the tread portion. This increases the critical speed for the generation of standing waves and suppresses their generation.

This makes it possible to prevent standing waves generated in the tread portion from being transmitted to the bead portions through the sidewall portions, thereby preventing repeated stress and deformation in the bead portions, thereby improving the durability of the bead portions.

In conventional cord physical properties, in addition to compressive stress in the cross-sectional direction of the folded part of the carcass cord at the bead part, complex stress was added due to standing waves.
By suppressing standing waves, the durability of the bead portion is further improved when an elastic cord is used.

[Example] An example of the present invention will be described below using a tire size of 46 x 17R20.
This will be explained based on the drawings, taking as an example the case of an aircraft tire.

In FIG. 1, which shows a state where the tire is mounted on a regular rim R and filled with the regular internal pressure, the radial tire 1 includes a bead portion 3 through which a bead core 2 passes, and a sidewall that is connected to the bead portion 3 and extends outward in the tire radial direction. section 4, and a tread section 5 connecting the outer ends of the sidewall section 4.

Furthermore, the tire 1 includes an inner layer 7A consisting of a plurality of carcass plies 7a, for example, four carcass plies 7a, in which a bead core 2 having a substantially circular cross section is folded from the inside to the outside of the tire, and a folded portion of the inner layer 7A. A carcass 7 is provided, which includes a plurality of carcass plies 7b, for example two carcass plies 7b, which are folded back from the outside to the inside of the enclosing tire. Further, each carcass cord of the carcass ply 7as7b is arranged in a radial direction having an inclination of 70 degrees to 90 degrees with respect to the tire equator CO, and in this example, the carcass 7 has a carcass cord between adjacent carcass plies. They are tilted alternately across the tire radial direction.

Further, a bead apex 9 made of tapered rubber extending in the radial direction of the tire is provided above the bead core 2 to increase rigidity and disperse stress due to bending of the folded portion of the carcass. Note that a chafer (not shown) for preventing rim displacement may be provided on the outer surface of the bead portion 3.

The tread portion 5 also includes a belt layer 1o located inside the carcass 7 at a cord angle of 0 to 20 degrees, preferably 0 to 5 degrees with respect to the tire equatorial plane.
In this example, between the belt layer 10 and the carcass 7, one or more cut breakers 14 are arranged at a cord angle of 5 to 40 degrees with respect to the tire equatorial plane.
The cut breaker 14 is used to improve cornering force performance. Naorit bougie force braai 14
By providing this on the outside of the belt layer 1o, the cornering force can be improved and it can also function as a protective layer for the belt layer 10. It can also be installed both inside and outside.

Furthermore, the belt layer 10 is made up of a plurality of belt plies 10a, for example, 6 to 10 belt plies 10a, and the belt plies 10a are gradually sandwiched outward in the radial direction. has a trapezoidal cross section including the tire axis, and its side surface tab is an inclined surface substantially along the outer surface SB of the tire buttress portion. Also belt layer 1o
The width W, that is, the maximum weight of the belt layer 10, the width of the innermost ply 10a in this example, is set in a range of about 75 to 85% of the tire hit.

Further, in the present invention, in FIG. 2, the equatorial height Hl, which is the height in the radial direction from the bead bottom surface at the equatorial point P1, which is the point where the radial inner surface E of the belt layer 10 intersects with the tire equatorial plane co, is: The outermost point of the inner surface E in the tire axial direction is greater than the outer end height H2 which is the height in the radial direction at the outer end point P2 of the inner surface E, and the outer end height is greater than the equator height Hl and the outer end height. The belt camber amount H, which is the difference (Hl-H2) from the belt width H2, is set to 6% or more of the belt width W, which is the length in the tire axial direction between the outer end points P2.22.

This means that in a conventional high-speed heavy-load radial tire, the ratio of the belt camber amount H to the belt width W is 5.
．． This is different from setting it at 5% or less.

In the tire 1, the radius of curvature R1 of the curved surface F of the center line passing through the mid-thickness position of the carcass 7 along the inner surface E of the belt layer 10 is determined by the camber as shown by the broken line and the dashed line in FIG. -Curved surfaces Fa, F of conventional tires with smaller amount H
It is smaller than the radius of curvature R1a and Rlb of b.

As mentioned above, this causes the crown portion 2o to protrude radially outward relative to the shoulder portion 21, and the tension T caused by the centrifugal force in the center portion 2o during high speed rotation in the evening and early evening. is relatively increased compared to the shoulder portion 21. This helps improve the critical speed of the standing wave.

Further, the tire 1 having the belt layer IO having such a small radius of curvature R1 is formed by molding in a vulcanization mold in which the portion where the tread surface is formed has a relatively small radius of curvature.

Further, the carcass 7 is moved from the outer end point P2 to the bead core 2.
Until then, the vulcanization mold is set so as to form a smooth curved surface based on the so-called natural equilibrium shape theory. In this way, the radius of curvature R2 of the curved surface G centering on the sidewall portion 4 of the tire of the present invention is based on the natural equilibrium shape theory, and the curved surfaces Fa, , Fb of the conventional tires IA and 1B are also based on the natural equilibrium theory. The radii of curvature R2aSR2b have approximately the same size, so the curved surface F of the carcass 7 of the tire 1 of the present invention is located inward in the tire axial direction compared to the curved surfaces Fa and Fb of the conventional tire.

The fact that the curved surface F of the carcass 7 is located inward in the tire axial direction as described above means that the curved surface F is the curved surface Fa of the conventional tire.
The angle α between the tangential line that is in contact with the bead core 2 and the line in the axial direction of the tire is higher than that of the conventional tire IA.
,, IB connection at a.

This is larger than the angles αa and αb of tb.

Such a rise occurs from the flange F of the rim to the curve m.
It is clear that this will push F away.

As a result, when the tire 1 of the present invention is mounted on a regular rim R and filled with the regular internal pressure, when it falls under a load, the contact pressure at the upper end of the rim flange C is lower than that of the conventional tire. It is clear that this can be reduced compared to the previous year.

As shown in FIG. 3 in detail, the contact pressure is 1.2 times the radius of curvature r on the upper piece formed horizontally at the upper end of the rim flange C via a circular arc portion with a radius of curvature r. It is preferable that the contact pressure at the separating point P3 be 30 kg/cd or less when a load twice the normal load is applied. By lowering the contact pressure in this way, the bending portion The bending stress acting on the bead portion 3 and the compressive stress acting on the carcass cord due to the reaction force due to the contact pressure acting on the carcass cord can be reduced, and the durability thereof can be improved.

As mentioned above, the belt camber amount H is set to 6 of the belt width W.
%, the contact pressure can be increased to 30 kg/cm”
The bending stiffness of the bead reinforcement portion such as the bead apex 9 is adjusted so as to easily achieve the following and to obtain this contact pressure.

The radius of curvature R1 for obtaining the rise is determined by the belt camber amount H and the belt width W.

Furthermore, making the radius of curvature R1 small means that, as shown in FIG.
Compared to conventional tires, the carcass cord bus l on one side, which is the length of the carcass 7 in the tire axial cross section leading to O, is
This results in a reduction of about 1.5 to 4%, preferably about 2.5 to 3%.

In addition, the above-mentioned tire has a tread shape with a convex center, which results in an improvement in the shape of the ground contact surface.

- From this point of view, the ratio is set to 6% or more.

However, when the ratio exceeds 20%, the tire's equatorial CO portion protrudes, which tends to cause uneven wear and makes manufacturing difficult. Therefore, the range is 6% or more, preferably 2%.
It is 0% or less, more preferably 11% or less and 7% or more.

Highly stretchable elastic cord is used for the carcass cord.

The elastic cord has an elongation S5 (%) of 5 when loaded with 5 kg.
or more and 10 or less (preferably 5 to 8), and elongation S, 5 (X) at a load of 10 kg to 9 or more and 15 or less (
Preferably 10-12), elongation S at 20 kg load, 5
(%) is set at 14-20.

In yet another example, the carcass cord has an elongation S at a 5 kg load divided by the denier of the cord.

7.35×1014 or more and 14.7kg×1014
The following shall apply. In addition, the elongation at 10 kg load SIO divided by the code denier number D10, the elongation at 20 kg load St
D is the value obtained by dividing O by the denier number of the cord! , respectively.
13.2×1014~22.1×10-', 20.5
X 10″4 to 29.4×1014.

Such elastic chords are shown in FIGS. 4(A) and 5(B), with each lower limit of the song, mal, a2, and upper limit of the curves b1 and b2.
A zero-elastic cord with the characteristics of the region sandwiching the curve a,
As shown in b (combining curves al and a2, a, bl, and b2 are collectively referred to as b), the elongation is large under a small load, and as the load increases, the elongation rate decreases. It is growing.

By using an elastic cord having such characteristics, the carcass cord is subjected to a large elongation at the initial stage of internal pressure filling together with the internal pressure filling.

When the load further increases to 10 kg and 20 kg, the carcass cord stretches as the load increases, but the elongation rate gradually decreases.

Furthermore, as shown by curve C, the conventional cord has a larger rise than curve A and is almost linear, and when using such a conventional cord, the elongation of the carcass cord is small even when the internal pressure is filled. However, it is inferior in its ability to relieve the compressive stress that acts upon deformation.

In contrast, since the elastic cord has the characteristics of the region between the curves vAa and 5, it is possible to improve the durability of the tire.

Naori-cascode, 5 kg, preferably 10 dazzles, 2
The regulations regarding the elongations S II , S l@, and SXO under a load of 0 kg define the values of the elongation of the cord due to the load, regardless of the denier number of the carcass cord used. On the other hand, the other regulation is 5 kg.
The value obtained by dividing the elongation under load S, by the denier number, therefore defines the elongation under a load of 5 kg per denier, and therefore the second
It means the elongation rate when a 5 kg load is applied per 1 denier of the cord.The carcass cord is understood mainly from the characteristics of the cord, and therefore it is used in a wide range of heavy-duty, high-speed tires, including aircraft tires. The former, which is adopted and defines only the elongation under a predetermined load, defines a value that can be suitably used mainly as an aircraft tire, and moreover, as a tire for a large jet aircraft.

Furthermore, the initial elastic modulus of the elastic cord E s (kg/gII
”) is 130 or more (preferably 140 or more) and 200
The following shall apply.

The initial elastic modulus E s (kg/ms") is the load (kg) measured using a constant-speed extension type tensile tester, as shown in Figure 5.
, draw an elongation (%) curve d, and the above song 1 at elongation of 7%.
It is a value defined as the slope of the tangent line It can add elongation to the cord.

Furthermore, the elastic cord has a load at break, that is, a cord strength of 30 kg or more, preferably 40 kg or more and 6
Those weighing about 0 kg or less can be suitably used.

Further, as the elastic cord, a nylon cord, a polyester cord, an aromatic polyamide cord, a carbon cord, a metal cord, or a hybrid cord of two or more kinds of cords is used.

Furthermore, when using a cord with such physical properties, the tension in so-called depth stretching, in which tension and heat are applied to the cord for a predetermined period of time, is lower than the tension used in conventional depth stretching. It can be obtained by reducing it to a large amount. In order to improve this property, for example, when using a nylon cord, the number of twists per 103
I, and the number of twists is increased compared to about 23 T/l0CI, which is conventionally done. In addition, by giving a walnut to the cord, such as mixing cords with a small elongation rate and cords with a high elongation rate, and pre-coiling the cords with a small elongation rate, the cord will have a small elongation rate when the load reaches a predetermined value. It is also possible to form the cord so that the load is applied to the cord, thereby reducing the elongation rate as a whole.

By using such an elastic cord as a carcass cord, it is possible to bulge the belt layer 10 during normal internal pressure filling, and it becomes easy to vary the belt camber amount H described above.

Further, the carcass cords form the carcass plies 7a, 7b by being embedded in the base rubber. The base rubber used is one that exhibits the characteristics of the cord in addition to reinforcing properties and low heat generation properties. As such, 50 to 70 carbon is added to a base material made of one or more of natural rubber and synthetic isoprene rubber. The quantity is mixed and the 100% modulus is 30 to 70 kg/ct+”
A material having an elongation at break of 200% or more and 500% or less is preferably used. If the amount of carbon is less than 50 parts by weight, reinforcing properties tend to decrease, and if it exceeds 70 parts by weight, heat generation tends to increase. 100% modulus is 30k
If it is less than "g/cm", the heat will increase and the weight will increase to 70 kg.
/cm", the reinforcing property tends to be low; if the elongation at break is less than 200%, the carcass has insufficient ability to follow the strain and tends to cause rubber breakage; and if it exceeds 500%, the heat generation is high. There is a tendency to

In this way, by giving a larger elongation in advance compared to conventional tires, the compressive stress of the carcass cord that occurs on the rim flange C side is reduced when the bead portion 3 is bent during takeoff and landing, and the compressive strain is reduced. This prevents deformation, local bending, and even breakage due to fatigue caused by compressive strain. Furthermore, the compressive stress of the rubber itself in the bead portion 3 can be alleviated, and the durability of the bead portion can be reduced by, for example, 10%.
It is possible to improve beyond that.

It is preferable that the belt cord 11 is made of a cut breaker cord and a carcass cord whose elongation changes under load are similar to those of the carcass cord.
The elongation S s (%) when loaded with kg is smaller than the carcass cord, and is 3 to 6, or the value obtained by dividing the elongation S5 (%) by the denier number (d), C%/d). 3.85×
1014 to 7.69×1014. The seat breaker cord used has similar characteristics to the belt cord. Note that cords made of different materials may also be used.

Further, the belt cord 11 and the cut breaker 14 are embedded in the same base rubber as described above, and the belt ply 10a,
10b, forming a cut breaker ply 14a.

The belt cord 11 and the carcass cord are both relatively thick cords with the same diameter d11, for example, 1260 d/
A cord of about 2 to 2700 d/3 is used, and an auxiliary cord of the same diameter or a smaller diameter is used.

Furthermore, the belt layer 10 can also be formed as an endless type by a so-called cord winding method in which one or several cords are wound spirally.

[Example 1] A tire having the structure shown in FIG. 1 and having a tire size of 46×17R20 was manufactured as a prototype according to the specifications shown in Table 1.

We also produced trial tires shown in the comparison column. The symbol (A) for the braai structure in the same table indicates the type of braai structure shown in Table 3. Also, in Table 3, the same cut breaker cord as the belt cord is used. In addition to filling Tenju regular internal pressure, it also meets the National Civil Aviation Administration standard TSO-
Durability was tested based on a taxi simulation test based on C62c. The results are shown in the same table by factor.

Note that 61 indicates completion, and 200% after the test.
Items that withstood takeoff under load are marked with an O mark.

Further, regarding the tires of Example 2 and Comparative Example 1.2, 10
The temperature rise in the crown part, part of the shield, and the tail part was measured when the vehicle was running at 0% load and 3001a* per hour. In each case, a thermocouple was inserted at the mid-thickness position, and the temperature was measured after 1 hour of operation. In Example 2, the temperature of the bead portion is low.

Furthermore, the rotational speed was varied to determine the critical speed at which standing waves occur. The example product is approximately 300km/
I was able to achieve this in about an hour. The results are shown in an index format with Comparative Example 1 as 100, and the larger the value, the higher the critical velocity.

Further, the 100% load of Example 2 and Comparative Example 3, 200
Figure 6 (A) (E) shows the deformation profile at % load.
), and FIG. 7 shows the contact pressures at the 23 points on the rim flange and at the 25 points in the middle of the arc r.

It can be seen that the example product has a slightly upright shape and a low contact pressure.

[Example 2] Using ply specifications m (B) to (F) in Table 3,
The results of trial production of tires of Examples 4 to 7 and similar tests are also shown.

〔Effect of the invention〕

As described above, the tire of the present invention improves the durability of the bead portion by increasing the critical speed for generating standing waves and suppressing their generation.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a diagram showing the characteristics of the breaker and carcass in comparison with a conventional tire, Fig. 3 is a sectional view showing the bead portion, and Fig. 4 (A) (B
) is a diagram showing the cord characteristics, Figure 5 is a diagram explaining the initial elastic modulus, Figures 6 (A) and (B) are diagrams showing the deformation profile, and Figure 7 is an example of the measurement results of contact pressure. FIG. 8 is a diagram illustrating bead deformation. 2--Bead core, 3--Bead portion, 4--Side wall portion, 5--Tread portion, 7--Carcass, 10--Belt layer, 10a--Belt ply. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura Figure 1 Figure 2 Figure 3 Figure 4 (A) Inakabi 0/. 5th rM Figure 4 (B) 匈胛zo/Saku-ru x 10°4

Claims (1)

[Claims] 1. From the tread part to the sidewall part, turned back at the bead core of the bead part, and at an angle of 70 degrees to 9 degrees with respect to the tire equator.
A carcass consisting of one or more carcass plies having a carcass cord inclined at an angle of 0 degrees, and a belt layer using a plurality of belt plies disposed on the radially outer side of the carcass and inside the tread portion, and a regular rim. The equatorial height H1, which is the height in the radial direction at the point where the radial inner surface of the belt layer intersects with the tire equatorial plane, is equal to It is larger than the outer end height H2 which is the height in the radial direction, and the difference between the equator height H1 and the outer end height H2 (H1-H2
), the belt camber amount H is 6% of the belt width W, which is the length in the tire axial direction between the outer ends of the inner surface of the belt layer.
The above-mentioned high-speed heavy-load radial tire. 2. The belt layer comprises a plurality of belt plies made of belt cords that are inclined at an angle of 5 degrees or less with respect to the tire equator, and radially inward or outward with an angle of 5 degrees or more and 40 degrees or less with respect to the tire equator. 2. The radial tire for high-speed heavy loads according to claim 1, further comprising a cut breaker having an auxiliary cord inclined at an angle of . 3 The carcass cord has an elongation S_5 when loaded with 5 kg.
2. The high-speed heavy-load radial tire according to claim 1, wherein the high-speed heavy-load radial tire is made of an elastic cord having a ratio of 5 to 10 (%). 4 Elongation of the carcass cord when loaded with 5 kg S_5 (
%) is 5 to 8. The high speed heavy load radial tire according to claim 1. 5 Elongation S_1 of the carcass cord when loaded with 10 kg
_0 (%) is 9 to 15, elongation S when loaded with 20 kg
The high-speed heavy-load radial tire according to claim 1, characterized in that _2_0 (%) is 14-20. 6 The belt cord has an elongation S_5(
%) is 3 to 6. The high speed heavy load radial tire according to claim 2. 7 The carcass cord has elongation (%) when loaded with 5 kg.
The value D_5 (%/d) divided by the denier number of the cord is 7
．． The high-speed heavy-load radial tire according to claim 1, comprising an elastic cord having a diameter of 35 x 10^-^4 to 14.7 x 10^-^4. 8 Elongation (%) of the above carcass cord when loaded with 10 kg
D_1_0 (%/d) divided by the denier of the cord
is 13.2 x 10^-^4 to 22.1 x 10^-^4, and the value D_2_0 (%/d) obtained by dividing the elongation S_2_0 (%) with a 20 kg load by the denier number d of the cord is 20.
2. The high-speed heavy-load radial tire according to claim 1, wherein the tire has a diameter of 6×10^-^4 to 29.4×10^-^4. 9 The value D_5 (%/d) obtained by dividing the elongation (%) of the belt cord at a load of 5 kg by the denier number d of the cord is 3.
3. The high-speed heavy-load radial tire according to claim 2, wherein the tire has a diameter of 85 x 10^-^4 to 7.69 x 10^-^4. 10 Elongation (%) of the belt cord when loaded with 10 kg
The value D_1_0 (%/d
) is 6.41 x 10^-^4 ~ 10.26 x 10^1^
4, and the value D_2_0 (%/d) obtained by dividing the elongation (%) under a load of 20 kg by the denier number d of the cord is 10.26.
3. The high-speed heavy-load radial tire according to claim 2, wherein the tire has a diameter of x10^-^4 to 17.59 x 10^-^4.